This revised application seeks support under the NCRR Shared Instrumentation Grant (SIG) program to update the department's multi-user confocal microscopy imaging facility. This facility currently houses a Bio-Rad 1024 MP scanhead on a fixed stage upright microscope (Olympus BX50) with a Kr/Ar laser (Bio-Rad) used for conventional single-photon confocal microscopy. In 2004, Carl Zeiss acquired the Cell Science division of Bio-Rad, and as a result, support for the hardware and software on our current system is being phased out. By 2007, there will be no service contract and the availability of parts is not guaranteed. Moreover, we have been unable to identify a third party vendor who could offer service and maintenance. Because user time on other confocal imaging systems within the University is either severely limited or unavailable, the acquisition of a new, fully supported confocal imaging system is critical for continued progress on the imaging aspects of the NIH funded research projects in the Department. We identified the Zeiss LSM 510 as an appropriate replacement because it offers state-of- the-art performance and sufficient versatility to meet the needs of multiple users. Finally, Zeiss is offering a substantial discount to encourage Bio-RAD users to migrate to the Zeiss instrument, and we do not know how long this policy will remain in effect. The Department of Neurobiology and Anatomy has committed significant space and support to the confocal imaging suite. In addition, the University has committed funds towards the maintenance contract of the instrument. The current system is housed in a 245 sq ft. room that has been extensively renovated to meet the needs of the instrument. The ventilation system was enhanced to provide constant temperature and low humidity. The electrical system was enhanced to isolate sensitive instrumentation from power supplies that produce line spikes. An adjacent room was remodeled to provide a convenient location for off-line analysis of confocal data. In addition, the Department has an established organizational structure and user-sharing system, which will be continued. Thus, institutional support for the confocal imaging core is already in place. Relevance: The focus of the user group is on signaling cascades and changes in morphology in individual neurons. Confocal microscopy is an essential tool for the investigation of these fundamentally important processes in neurobiology. [unreadable] [unreadable] [unreadable]